Electrometallurgical treatment of zinc ores and especially blende.



UNITED ST TES OONSTANTIN JEAN TOSSIZZA, OF PARIS, FRANCE.

ELECTROMETALLURGICAL TREATMENT OF ZINC ORES AND ESPECIALLY BLENDE.

SPECIFICATION forming part of Letters Patent No. 703,857, dated July 1, 1902. Application filed August 6,1901. Serial No. 71,105. (No specimens.) 1

T0 aZZ whom it may concern:

Be it known that I, OoNsrANTIN JEAN Tos- SIZZA, engineer, a citizen of the French Republic, residing at Paris, France, have invented certain Improvements in Electrometallurgical Treatment of Zinc Ores and Especially Blende, of which the following is a specification. 4

In my application for Patent No. 71,104, filed August 6, 1901, I have described a process for the electrolysis of the salts of copper in which sulfuric acid is employed to lower the electromotive force necessary to the electrolysis. In effect, the action of the electric current oxidizes about the anode the sulfurous acid dissolved in the electrolyte, transforms it into sulfuric acid, and thus gives rise to an electromotive force-of about ninetenths volt favorable to the reaction. The minimum tension necessary for the electrolysis of salts of copper is thus lowered from 1.21 volts to thirty-one one-hundredths Volt. It is evidently very desirable to generalize this process for other metals, particularly when these metals exist in nature in the state of sulfid ores, (susceptible of furnishing all the sulfurous acid necessary,) as is, for example, the case of zinc; but for this metal the direct application of the process encounters the following diificulty: When a saline solution charged with sulfurous acid is subjected to electrolysis, care must be taken not to exceed at the poles of the electrolytic cell a voltage of about one volt, for above this limit the acid is decomposed in the medium of the electrolyte, giving rise to the production of hydrogen sulfid and even of sulfur. This difficulty is easily avoided with copper, (since the electrolysis of it is possible, as we have said, commencing with thirty-one onehundredths volt;) but it is not so with zinc. In fact, the minimum voltage of decomposition of the salts of zinc being about two and three-tenths volts the presence of the sulfurous acid can lower it only to one and fourtenths volts. Such then would be the minimum tension which must be employed at the poles of the electrolytic cell, and one sees that it would be too high to be utilized without giving rise to the decomposition of the sulfurous acid. If to this it is added that sulfurous acid yields with zinc hydrosulfurous acid, one may be perfectly sure that the direct application of the process is impossible. Under these conditions it is necessary to divide the operation into two parts.

The first part consists in the electrolysis of the salt of zinc-sulfate, for examplewith employment of soluble anodes of pure copper in any known arrangement of apparatus. Thus metallic zinc is obtained at the cathode, while the anode dissolves with production of copper sulfate. The voltage necessary for the operation is one and one-tenth volts at the minimum and rises for currents of practically acceptable intensity (forty amperes per square meter) to one and five-tenths volts about. This first operation, although producing zinc electrolytically, would be by itself alone industrially inapplicable, since it would necessitate the definite transformation into the condition of salt of quantities of copper corresponding with the zinc obtained.

The second operation has for its object to reconstitute the anode-plates of copper par- To tially dissolved in the first operation. this end they are used as cathodes in an electrolytic operation, wherein the anodes are insoluble and wherein the electrolyte is formed of thesulfate of copper produced inthefirst operation and is preliminarily charged with sulfurous acid. The copper is deposited at a minimum voltage of thirty-one one-hundredths volt and for practically acceptable intensities at a voltage of about five-tenths volt. An acid liquid is obtained containing all the sulfuric acid from the decomposition of the sulfate plus that from the oxidation of the sulfurous acid, which liquid serves to dissolve a new lot of zinc ore.

Taken'together, the two operations permit the electrolysis of the zinc at a voltage which is the sum of those of the two operationssay, at a minimum one and four-tenths Volts or with practically acceptable intensities two volts.

The subdivision of the operation into two parts has no other object and effect than to prevent the decomposition in the medium of the electrolyte of the sulfurous acid, and thus permitting the lowering of voltage which it produces to be utilized. It is also to be noted that as well in the one as in the other of the two operations there is no polarization. The

subdivision into two operations has thus allowed the depolarizing properties of sulfurous acid (known properties) to be utilized in cases where it would otherwise have been impossible to apply them-namely, in the case of the salts of zincfor the reasons which I have enumerated at the beginning. The depolarizing properties of the sulfurous acid and the resultant lowering of voltage are evidently retained, whatever may be the nature of the salt of zinc subjected to the electrolysis. It is evident also that the method hereinabove indicated is general and can be applied to all metals having high voltages of electrolytic decomposition and being susceptible of deposition at the cathode in metallic form-as, for example, nickel, cobalt, cadmium.

I claim as my invention and discovery- 1. For the electrolysis of the sulfate and other salts of zinc, the process whereby a practical reduction of the voltage below two and three-tenths volts is obtained by the aid of sulfurous acid as a depolarizer, the said process being divided into two parts to avoid the decomposition of said sulfurous acid and consisting as to one part in the electrolysis of the zinc salt with corresponding solution of copper anodes and formation of copper salt, and as to the second part in the electrolytic reconstitution of the said copper anodes by decomposition of the so-formed copper salt in a solution preliminarily charged with sulfurous acid, substantially as described.

2. For the electrolysis of metals, to wit, nickel, cobalt, cadmium, and the like, as well as zinc, which can be electrolytically deposited in metallic form at the cathode and whose salts have a voltage of decomposition too high to avoid the decomposition of sulfurous acid in the medium of the electrolyte, the process whereby said electrolysisv is practically effected with a voltage effectively lowered by the employment of sulfurous acid as a depolarizer, the said process being divided into two parts to avoid the decomposition of said sulfurous acid and consisting as to one part in the electrolysis of the salt ofsuch a metal with corresponding solution of copper anodes and formation of copper salt, and as to the second part in the electrolytic reconstitution of the said copper anodes by decomposition of the so-formed copper salt in a solution preliminarily charged with sulfurous acid, substantially as described.

In witness whereof I have hereunto signed my name in the presence of two subscribing witnesses.

CONSTANTIN JEAN TossIzZ'A.

Witnesses:

JULEs ARMENGAUI), J eune, MARCEL ARMENGAUD, J eune.

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